Stop the Plan page unmounting on every wish mutation

useLeaveWishes.fetch() runs again after every add/update/remove to
refresh the list, and it flipped the same isLoading flag the initial load
uses. Plan.tsx swaps the whole page for a spinner on that flag, so every
mutation unmounted and remounted WishEditor -- wiping which rows were
expanded and any save status.

This predates auto-save (the old manual Save button did it too), but a
debounce that fires on every edit turned an occasional flicker into the
dominant experience, collapsing the row the user was editing.

A background refetch now toggles a separate isRefreshing flag; isLoading
stays true only for the initial load. Plan.tsx needed no change once the
hook was right.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RXMhc9nT6sNz1SL4j8dznL

frontend/src/pages/Plan.test.tsx

@@ -1,5 +1,5 @@
 import { describe, it, expect, beforeEach, vi } from 'vitest'
-import { render, screen, fireEvent, waitFor } from '@testing-library/react'
+import { render, screen, fireEvent, waitFor, act } from '@testing-library/react'
 import { Plan } from './Plan'
 import * as hooks from '@/hooks'
 import { useWorkspace } from '@/context'
@@ -156,6 +156,7 @@ describe('Plan', () => {
     vi.mocked(hooks.useLeaveWishes).mockReturnValue({
       data: [mockWish],
       isLoading: false,
+      isRefreshing: false,
       error: null,
       refresh: vi.fn(),
       add: mockAddWish,
@@ -188,6 +189,42 @@ describe('Plan', () => {
     expect(screen.getByText(/Laddar planering/)).toBeInTheDocument()
   })
 
+  it('renders the loading spinner during the initial wishes load, before any data has arrived', () => {
+    vi.mocked(hooks.useLeaveWishes).mockReturnValue({
+      data: [],
+      isLoading: true,
+      isRefreshing: false,
+      error: null,
+      refresh: vi.fn(),
+      add: mockAddWish,
+      update: mockUpdateWish,
+      remove: mockRemoveWish,
+    } as any)
+    renderPlan()
+    expect(screen.getByText(/Laddar planering/)).toBeInTheDocument()
+    expect(screen.queryByTestId('wish-editor')).not.toBeInTheDocument()
+  })
+
+  it('does not show the full-page spinner or unmount the wish editor during a mutation background refresh', () => {
+    // useLeaveWishes flips isRefreshing (not isLoading) while it refetches
+    // after add/update/remove. Plan must keep rendering the wish editor
+    // (and whatever expanded/save-status state it holds) through that.
+    vi.mocked(hooks.useLeaveWishes).mockReturnValue({
+      data: [mockWish],
+      isLoading: false,
+      isRefreshing: true,
+      error: null,
+      refresh: vi.fn(),
+      add: mockAddWish,
+      update: mockUpdateWish,
+      remove: mockRemoveWish,
+    } as any)
+    renderPlan()
+    expect(screen.queryByText(/Laddar planering/)).not.toBeInTheDocument()
+    expect(screen.getByTestId('wish-editor')).toBeInTheDocument()
+    expect(screen.getByTestId('wish-card-lw1')).toBeInTheDocument()
+  })
+
   it('renders the page title and the wish editor', () => {
     renderPlan()
     expect(screen.getByRole('heading', { name: 'Planering', level: 1 })).toBeInTheDocument()
@@ -246,9 +283,20 @@ describe('Plan', () => {
   it('edits and removes a wish through the wish editor', async () => {
     renderPlan()
 
+    // WishEditor auto-saves edits after an 800ms debounce (no per-row Save
+    // button anymore) — advance fake timers to let it fire.
+    vi.useFakeTimers()
     fireEvent.change(screen.getByTestId('wish-weeks-lw1'), { target: { value: '8' } })
-    fireEvent.click(screen.getByTestId('wish-save-lw1'))
-    await waitFor(() => expect(mockUpdateWish).toHaveBeenCalledWith('lw1', expect.objectContaining({ targetWeeks: 8 })))
+    act(() => {
+      vi.advanceTimersByTime(800)
+    })
+    expect(mockUpdateWish).toHaveBeenCalledWith('lw1', expect.objectContaining({ targetWeeks: 8 }))
+    // Flush the microtask queue so Plan's `.finally(() => setIsSaving(false))`
+    // runs and re-enables the remove button before it's clicked below.
+    await act(async () => {
+      await Promise.resolve()
+    })
+    vi.useRealTimers()
 
     fireEvent.click(screen.getByTestId('wish-remove-lw1'))
     await waitFor(() => expect(mockRemoveWish).toHaveBeenCalledWith('lw1'))
@@ -263,6 +311,51 @@ describe('Plan', () => {
     await waitFor(() => expect(screen.getByTestId('wish-error')).toHaveTextContent('nätverksfel'))
   })
 
+  it('shows a generic error banner when adding a wish fails with a non-Error value', async () => {
+    mockAddWish.mockRejectedValue('boom')
+    renderPlan()
+
+    fireEvent.click(screen.getByTestId('wish-preset-sommar'))
+
+    await waitFor(() =>
+      expect(screen.getByTestId('wish-error')).toHaveTextContent('Kunde inte lägga till önskemål'),
+    )
+  })
+
+  it('shows a calculating label on the propose button while a proposal is in flight', () => {
+    vi.mocked(hooks.usePlanProposal).mockReturnValue({
+      data: null,
+      isLoading: true,
+      error: null,
+      propose: mockPropose,
+    } as any)
+    renderPlan()
+    expect(screen.getByTestId('propose-plan-button')).toHaveTextContent('Beräknar')
+  })
+
+  it('treats a missing workspace as having no workspace id: skips the wish editor and refuses to apply', async () => {
+    vi.mocked(useWorkspace).mockReturnValue({ ...mockWorkspaceContext, workspace: null } as any)
+    vi.mocked(hooks.usePlanProposal).mockReturnValue({
+      data: mockProposal,
+      isLoading: false,
+      error: null,
+      propose: mockPropose,
+    } as any)
+    renderPlan()
+
+    // workspace?.id ?? null falls back to null, so the wish editor (guarded
+    // on workspaceId) must not render even though wishes/members data exist.
+    expect(screen.queryByTestId('wish-editor')).not.toBeInTheDocument()
+
+    fireEvent.click(screen.getByTestId('plan-apply-button'))
+
+    await waitFor(() => {
+      // handleApplyPlan's `if (!workspaceId) throw` fires before ever
+      // reaching the real apply() call.
+      expect(mockApply).not.toHaveBeenCalled()
+    })
+  })
+
   it('shows an error banner when the proposal fails', () => {
     vi.mocked(hooks.usePlanProposal).mockReturnValue({
       data: null,